Staphylococcus epidermidis' Overload During Suckling Impacts the Immune Development in Rats

Area of Science:

• Microbiology
• Immunology
• Developmental Biology

Background:

• Mastitis, an inflammation of the mammary gland, affects 3-33% of breastfeeding mothers, often caused by Staphylococcus bacteria.
• Bacterial overgrowth in breast milk during mastitis can alter milk microbiota, potentially impacting the infant's immune development.
• Staphylococcus epidermidis is a common cause of infectious mastitis, mimicking clinical or subclinical conditions.

Purpose of the Study:

• To investigate the short- and long-term effects of Staphylococcus epidermidis overload on the developing immune system in rats.
• To compare the impact of low-dose (subclinical mastitis) and high-dose (clinical mastitis) S. epidermidis exposure during the suckling period.
• To analyze changes in body metrics, gut health, hematology, and immune cell profiles.

Main Methods:

• Suckling rats were supplemented daily with low (Ls) or high (Hs) doses of S. epidermidis from day 2 to 21.
• Body weight and fecal humidity were monitored throughout the study.
• Morphometry, hematological variables, intestinal gene expression, immunoglobulin and cytokine profiles, and spleen cell phenotypes were assessed on days 21 and 42.

Main Results:

• While body weight remained unchanged, both Ls and Hs groups exhibited increased body length and reduced fecal humidity.
• Both doses led to minor alterations in lymphocyte subpopulations, decreased plasma immunoglobulin levels, and a Th2-biased immune response.
• High-dose exposure resulted in leukocytosis, lymphocytosis, and influenced intestinal barrier maturation, while the low dose affected T-cell homing patterns.

Conclusions:

• Staphylococcus epidermidis overload during suckling, even at low doses, significantly impacts the development of the immune system in rats.
• Both short-term and long-term immune dysregulation were observed, highlighting the vulnerability of the developing immune system to bacterial challenges.
• These findings suggest potential implications for infant health and immune function following maternal mastitis.